Verbs describe actions like going, seeing, eating, sleeping, wanting, and so on.
Verbs generally have three parts: the root, the stem, and the ending.
Roots
Just as flowers, fruits, and leaves grow from the same tree, so too do all kinds of Sanskrit verbs grow from a single root sound.
Usually, there is a clear root we can identify. For example, tradition says that the root of the words khādāmi ("I eat"), khāditam ("eaten"), and khāditum ("to eat") is just khād. But not all verbs are so simple. Very common verbs tend to be irregular, and it is not initially obvious what root they come from.
Stems
To create different words from our verb root, we add different groups of sounds to the end of it. This creates a verb stem, from which the rest of the verb grows.
Here are some example verb stems:
khād + a ⟶ khāda, which is used for words like khādāmi (I eat), khādantu (may they eat), and so on.
khād + iṣya ⟶ khādiṣya, which is used for words like khādiṣyāmi (I will eat).
khād + aya ⟶ khādaya, which is used for words like khādayāmi (I make someone eat).
Most stem patterns have a fixed meaning. iṣya and sya always create a verb that describes future events. aya usually creates a verb that implies "making" or "causing" someone to do something.
Endings
Verb endings show several different kinds of information, but two are most important:
the person of the verb, which shows what kind of person is doing the action ("I", "you", "he / she / it")
the number of the verb, which shows how many people are acting ("I", "the two of us", "all of us")