Этот рюкзак легче, чем мой чемодан.

In Russian, the verb to be is usually omitted in the present tense.

So:

• Этот рюкзак легче, чем мой чемодан.

literally looks like:

• This backpack lighter than my suitcase.

But in natural English, that means:

• This backpack is lighter than my suitcase.

This is completely normal in Russian.

Because рюкзак is a masculine singular noun, and этот must agree with it.

Russian demonstratives change form to match the noun’s:

• gender
• number
• case

Here:

• этот = this for a masculine singular noun
• рюкзак = masculine singular

Compare:

• этот рюкзак = this backpack
• эта сумка = this bag
• это окно = this window

For the same reason: чемодан is also a masculine singular noun, so the possessive my has to match it.

So:

• мой чемодан = my suitcase

Compare:

• моя сумка = my bag
• моё пальто = my coat

Russian possessives agree with the noun they describe.

Because the sentence is making a comparison.

• лёгкий = light
• легче = lighter

So:

• Этот рюкзак лёгкий. = This backpack is light.
• Этот рюкзак легче, чем мой чемодан. = This backpack is lighter than my suitcase.

When Russian compares two things, it often uses the comparative form of the adjective, just like English uses lighter, bigger, faster, and so on.

Yes, from a learner’s point of view, it is something you should simply memorize.

The base adjective is:

• лёгкий = light

But the comparative is:

• легче = lighter

So the form does not come from just adding one simple ending mechanically. There is a stem change, and this happens with a number of Russian adjectives.

It is best to learn:

• лёгкий → легче

as a pair.

Yes. Легче can mean either:

• lighter in weight
• easier

The meaning depends on context.

Examples:

• Этот рюкзак легче. = This backpack is lighter.
• Эта задача легче. = This problem is easier.

In your sentence, because it compares a backpack and a suitcase, the meaning is clearly lighter, not easier.

Here чем means than.

It is the standard word used in comparisons after a comparative adjective:

• лучше, чем... = better than...
• быстрее, чем... = faster than...
• легче, чем... = lighter than...

So:

• Этот рюкзак легче, чем мой чемодан. = This backpack is lighter than my suitcase.

Yes, you can also say:

• Этот рюкзак легче моего чемодана.

That is a very common alternative.

So Russian has two common ways to express this comparison:

1. легче, чем мой чемодан
2. легче моего чемодана

In the first version, чем means than, and the noun phrase stays in the straightforward form:

• мой чемодан

In the second version, there is no чем, and the compared noun goes into the genitive:

• моего чемодана

Both are natural. The чем version is often especially clear for learners because it matches English structure more closely.

In standard written Russian, a comma is normally used before чем in a comparison like this.

So:

• Этот рюкзак легче, чем мой чемодан.

That comma helps mark the comparison part:

• чем мой чемодан = than my suitcase

So if you are writing this sentence, using the comma is the safe and standard choice.

Yes, Russian word order is more flexible than English word order, but the version you have is the neutral, standard way to say it:

• Этот рюкзак легче, чем мой чемодан.

That order is natural because it goes:

1. the thing being discussed
2. the comparative adjective
3. the comparison

You can change word order for emphasis, but that often sounds more marked or stylistic. For a learner, the given order is the best one to use first.

The stress is:

• Э́тот рюкза́к ле́гче, чем мой чемода́н.

A rough pronunciation guide:

• EH-tət ryuk-ZAK LYEKH-che, chem moy che-ma-DAN

A few helpful notes:

• рю in рюкзак sounds roughly like ryu
• ле́гче is pronounced with a kh/ch-like cluster, not like the English word leg
• the stress in чемодан is on the last syllable: чемода́н

Word by word:

• Этот = this
• рюкзак = backpack
• легче = lighter
• чем = than
• мой = my
• чемодан = suitcase

So the structure is:

• This backpack lighter than my suitcase

And natural English adds is:

• This backpack is lighter than my suitcase.