Learn Polish: To jest ucho.

When introducing something with the phrase "This is...", Polish always uses the word to, regardless of whether the noun that follows is masculine, feminine, or neuter. So, to jest is a fixed phrase meaning "this is".

What gender is the word ucho?

It is a neuter noun. A good hint for beginners is that most Polish nouns ending in -o (like ucho or okno) are neuter.

Could I just say To ucho without the word jest?

Yes! In Polish, it is very common to drop the verb jest (is) in simple "This is..." sentences. Saying To ucho is perfectly natural and means exactly the same thing.