Pour l’encourager pendant la promenade, Marie lui donne une petite friandise.

Pour l’encourager literally means to encourage him/her/it or in order to encourage him/her/it.

French often uses pour + infinitive to express purpose:

• pour manger = to eat / in order to eat
• pour aider Marie = to help Marie
• pour l’encourager = to encourage him/her

So in this sentence, Pour l’encourager pendant la promenade gives the reason for what Marie does: she gives a small treat in order to encourage the animal/person during the walk.

The l’ is a shortened form of le or la placed before a vowel sound.

Since encourager begins with a vowel, French contracts:

• le encourager → l’encourager
• la encourager → l’encourager

So l’ can mean:

• him
• her
• sometimes it

You cannot tell from l’ alone whether it refers to a masculine or feminine noun/person; context tells you.

l’ is the direct object pronoun of encourager. It means the being Marie wants to encourage.

So:

• Pour l’encourager = To encourage him/her/it

In context, this is often an animal being walked, such as a dog, but grammatically it could also refer to a person.

This is because the verb donner usually works with:

• a thing that is given = direct object
• the person/animal receiving it = indirect object with à

So:

• Marie donne une petite friandise à son chien. = Marie gives a small treat to her dog.

When à son chien becomes a pronoun, French uses lui:

• Marie lui donne une petite friandise. = Marie gives him/her/it a small treat.

So here:

• une petite friandise = what is given
• lui = the receiver

That is why lui is correct.

lui here means to him, to her, or sometimes to it.

It is an indirect object pronoun. In English, we often just say him or her after give, but French grammar treats this as give something to someone.

Compare:

• Je donne le livre à Marie. = I give the book to Marie.
• Je lui donne le livre. = I give her the book.

So in your sentence:

• Marie lui donne une petite friandise
  = Marie gives him/her a small treat

In French, object pronouns usually come before the conjugated verb.

So instead of English word order:

• Marie gives him a treat

French says:

• Marie lui donne une friandise

This is standard pronoun placement:

• Je le vois = I see him/it
• Je lui parle = I speak to him/her
• Marie lui donne... = Marie gives him/her...

Pendant la promenade means during the walk.

It tells you when Marie gives the treat or when the encouraging happens. Grammatically, it is a time expression introduced by pendant.

• pendant = during
• la promenade = the walk

So:

• Pour l’encourager pendant la promenade
  = To encourage him/her during the walk

This phrase could be understood as modifying the whole action: Marie gives the treat during the walk, for the purpose of encouraging the animal/person.

La promenade means the walk, referring to a specific walk already understood from context.

French often uses the definite article where English might also use the:

• pendant la promenade = during the walk

If you said pendant une promenade, that would mean during a walk, less specific.

So la promenade suggests a particular walk the speaker has in mind.

Une petite friandise means a small treat.

Breakdown:

• une = a
• petite = small
• friandise = treat, tidbit, sweet reward

A friandise is often a little treat given as a reward, especially to a child or an animal.

The adjective petite comes before the noun because some common adjectives in French often go before the noun, including many adjectives of size such as:

• petit / petite
• grand / grande
• jeune
• vieux / vieille

So:

• une petite friandise = a small treat

In French, many adjectives come after the noun, but some common ones often come before it. Petit/petite is one of those common exceptions.

So French says:

• une petite friandise

not usually:

• une friandise petite

A useful learner rule is the common BAGS group, whose adjectives often come before the noun:

• Beauty
• Age
• Goodness
• Size

Since petite describes size, it naturally goes before the noun here.

Donne is the present tense form of donner for Marie (= elle).

Conjugation:

• je donne
• tu donnes
• il/elle donne
• nous donnons
• vous donnez
• ils/elles donnent

So:

• Marie donne = Marie gives / Marie is giving

In French, the present tense can often translate into English as either simple present or present progressive, depending on context.

Yes. That is often helpful for learners.

For example, if l’ and lui both refer to a dog:

• Pour encourager son chien pendant la promenade, Marie donne une petite friandise à son chien.

This is grammatically possible, but French often prefers pronouns instead of repeating the noun, so the original sentence sounds more natural:

• Pour l’encourager pendant la promenade, Marie lui donne une petite friandise.

Notice that both pronouns can refer to the same being:

• l’ = the one being encouraged
• lui = the one receiving the treat

Yes. That is exactly what can happen here.

They do different grammatical jobs:

• l’ = direct object of encourager
• lui = indirect object of donner

So the sentence can mean:

• To encourage him/her during the walk, Marie gives him/her a small treat.

In natural English, repeating him/her twice sounds normal enough, and in French it is also perfectly normal because the two pronouns belong to different parts of the sentence.

Yes. The sentence begins with an infinitive phrase of purpose:

• Pour l’encourager pendant la promenade

Then comes the main clause:

• Marie lui donne une petite friandise

French often puts this kind of purpose phrase at the start of the sentence to set up why the action is happening.

You could think of the structure like this:

• [Purpose] + [Main action]
• To encourage him/her during the walk, Marie gives him/her a small treat.

This word order is natural and common in both French and English.