Podložka pod myš je vedle počítačové myši.

Czech does not have articles like English the and a/an.

So Podložka pod myš je vedle počítačové myši can mean:

• The mouse pad is next to the computer mouse
• A mouse pad is next to a computer mouse

Which one sounds best depends on the context.

Literally, it is something like a pad/mat for under a mouse.

• podložka = pad, mat, base, support
• pod = under
• myš = mouse

As a whole, podložka pod myš is the normal Czech way to say mouse pad or mouse mat.

Because podložka pod myš is the name of the object, not a description of where it is right now.

So even if the mouse pad is currently lying next to the mouse, it is still called podložka pod myš.

English works the same way:

• a mouse pad is still called a mouse pad even if nothing is on it

Here myš is in the accusative singular, because pod in this kind of expression behaves like under in the sense of to put under or for use under.

The important thing is that for the noun myš, the nominative singular and accusative singular have the same form:

• nominative: myš
• accusative: myš

So you cannot see the case change from the ending here, but grammatically it is accusative.

Because vedle requires the genitive case.

So:

• vedle koho? čeho? = next to whom? what?
• myš → myši in the genitive singular

That is why we get:

• vedle počítačové myši = next to the computer mouse

Here it is singular.

That can be confusing, because myši can also be a plural form in other contexts. But in this sentence it must be genitive singular, because it follows vedle.

So:

• vedle počítačové myši = next to the computer mouse
• not next to the computer mice

Because both the adjective and the noun have to match the case.

The basic form is:

• počítačová myš = computer mouse
  nominative singular

After vedle, we need the genitive singular, so both words change:

• počítačové myši

So:

• počítačová myš = computer mouse
• vedle počítačové myši = next to the computer mouse

Myš by itself can mean either:

• a mouse as an animal
• a computer mouse

If the context is obvious, Czech speakers often just say myš for the computer device too. But počítačová myš makes it completely clear that we mean the computer accessory.

So in this sentence, počítačové myši is a more explicit form.

Je means is.

It is the 3rd person singular form of být = to be.

So:

• podložka = mouse pad
• je = is
• vedle počítačové myši = next to the computer mouse

Together:

• The mouse pad is next to the computer mouse

Yes. Czech word order is more flexible than English because the endings show the grammatical relationships.

This sentence has a neutral, straightforward order:

• Podložka pod myš je vedle počítačové myši.

But you could also say:

• Vedle počítačové myši je podložka pod myš.

That still means the same thing, but the emphasis is slightly different. The first version is the most natural if you are talking about the mouse pad as the topic.

Podložka is in the nominative singular.

It is the subject of the sentence — the thing that is somewhere.

So the structure is:

• Podložka pod myš = subject
• je = verb
• vedle počítačové myši = location phrase

In other words, the mouse pad is the thing being described.