Learn Hardcore Russian: Черепок лежит на столе. - The fired ceramic body is lying on the table.

Черепок usually means a shard, potsherd, or broken piece of pottery/clay. In some contexts it can also mean a broken fragment of something similar, but its most basic sense is a pottery shard.

It is a masculine noun.

Why does the sentence use лежит instead of a form of to be?

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

So instead of saying something like The shard is on the table, Russian often uses a more specific verb of position:

лежать / лежит = to lie / is lying
стоять / стоит = to stand / is standing
сидеть / сидит = to sit / is sitting

So Черепок лежит на столе is more literally:

The shard is lying on the table

This is more natural in Russian than using an explicit present-tense to be.

Why is it лежит?

Лежит is the 3rd person singular present tense of лежать (to lie).

It matches the subject черепок, which is singular:

я лежу = I am lying
ты лежишь = you are lying
он / она / оно лежит = he / she / it is lying
они лежат = they are lying

Since черепок is one thing, Russian uses лежит.