Makulo kaj grataĵo estas sur la tekruĉo.

Esperanto has no indefinite article. So:

• makulo = a stain
• grataĵo = a scratch

Esperanto only has the definite article la, which means the.

So it is normal to say Makulo kaj grataĵo... without any word for a.

La means the. It is used when the noun is definite or already identifiable in context.

So:

• la tekruĉo = the teapot
• makulo = a stain
• grataĵo = a scratch

This sentence treats the teapot as a specific, known object, but the stain and scratch are being introduced as unspecified things on it.

In Esperanto, the verb does not change for singular or plural.

So:

• li estas = he is
• ili estas = they are
• makulo estas = a stain is
• makulo kaj grataĵo estas = a stain and a scratch are

The same form, estas, is used in all these cases.

Because the sentence is talking about one stain and one scratch.

In Esperanto, singular nouns end in -o, and plural nouns end in -oj.

So:

• makulo = one stain
• makuloj = more than one stain
• grataĵo = one scratch
• grataĵoj = more than one scratch

Using kaj joins two singular nouns together: a stain and a scratch.

Because there is no direct object here.

The sentence is describing where something is:

• Makulo kaj grataĵo = the subject
• estas = are
• sur la tekruĉo = on the teapot

The accusative -n is usually used for:

• a direct object
• sometimes motion toward a place

But here, sur la tekruĉo describes location, not motion, so no -n is needed.

Because this sentence expresses position, not movement.

• sur la tekruĉo = on the teapot (already there)
• sur la tekruĉon would suggest movement onto the teapot

A useful contrast:

• La makulo estas sur la tekruĉo. = The stain is on the teapot.
• Mi metas la glumarkon sur la tekruĉon. = I put the sticker onto the teapot.

So in your sentence, sur la tekruĉo is correct because nothing is moving.

Yes. Esperanto word order is fairly flexible.

For example, these are both possible:

• Makulo kaj grataĵo estas sur la tekruĉo.
• Sur la tekruĉo estas makulo kaj grataĵo.

Both mean basically the same thing. The difference is mainly one of emphasis:

• starting with Makulo kaj grataĵo focuses first on what is there
• starting with Sur la tekruĉo focuses first on the location

Esperanto does not need a dummy subject like English there.

English often says:

• There is a stain on the teapot.
• There are a stain and a scratch on the teapot.

Esperanto can simply say:

• Makulo estas sur la tekruĉo.
• Makulo kaj grataĵo estas sur la tekruĉo.

So Esperanto often uses a straightforward subject + estas + location pattern where English uses there is/there are.

Grataĵo is built from smaller parts:

• grati = to scratch
• -aĵ- = a concrete thing, result, or manifestation
• -o = noun ending

So grataĵo is literally something like a scratched thing/result of scratching, which in normal English becomes a scratch or scratch mark.

This is a very common pattern in Esperanto: roots combine with endings and affixes to make vocabulary very systematic.

Tekruĉo is a compound word:

• te- from teo = tea
• kruĉo = jug, pitcher, pot

So tekruĉo is literally a tea-pot/jug, which gives teapot.

In Esperanto compounds, the last part usually tells you the basic category of the thing. Here, it is a kind of kruĉo.

The special letters are important:

• ĉ sounds like ch in church
• ĵ sounds like s in measure or j in French jour

So roughly:

• grataĵo ≈ gra-TA-zho
• tekruĉo ≈ te-KROO-cho

Also remember that Esperanto stress is always on the second-to-last syllable:

• graTAĵo
• teKRUĉo

Not in the same way.

• kaj = and
• kun = with

So:

• Makulo kaj grataĵo = a stain and a scratch
• makulo kun grataĵo would mean something more like a stain with a scratch, which is a different relationship

Here the sentence is simply listing two things, so kaj is the correct word.