Learn Russian: Ребёнок хочет плавать.

It follows the verb хочет (wants). Just like in English, when you have a verb of desire or ability followed by another action, the second verb stays in the infinitive (dictionary) form. You conjugate the first verb (хочет) to match the subject, and leave the second one alone (плавать).

How does the verb хотеть (to want) change for other people?

It is quite irregular! For singular subjects like I, you, and he/she/it, it goes: я хочу, ты хочешь, он/она/оно хочет. But for plural subjects, it changes its pattern completely: мы хотим, вы хотите, они хотят. Since ребёнок (the child) is a singular third person, we use хочет.

The word ребёнок has the letter ё. Does the stress always fall on that letter?

Yes! A handy rule in Russian is that if a word contains the letter ё, that syllable is always stressed. In everyday Russian writing, the dots are often dropped and it is written as ребенок, but it is still pronounced with the stress on the 'yo' sound.

Is ребёнок considered a masculine, feminine, or neuter word?