Translation:reading and writing
In English, when we want to talk about a thing generally, we use a noun without an article, like in the sentences singing relaxes me, and marriage helps people. In Arabic, al- is used instead.
Note singing (غناء) above is a verbal noun (i.e. a word derived from a verb, used to describe an action, but is not a verb because it tells us nothing about an event), so to say “I sing” by saying “أنا غناء” would mean you are the embodiment of singing. Instead, you must use a present tense verb to express the present continuous (things happening as you speak, temporary situations, definite future plans etc) in order to say I am singing.
Bonjour689181, Andrew's answer is good. You might also like to know - in case you meet the term - that another way to say "verbal noun" is "gerund". Also, if you do Duolingo on a computer, as opposed to a phone, each chapter has a section called "Tips", which is an explanation of the vocabulary and grammar introduced in that chapter. They're very good, and leave nothing unexplained.
I find thqt one tends to usr the definite in Arabic roughly as often as in French, in contrast to Spanish, where it is much less frequent, and English, where it is even less so.
Perhaps you could judge that you should use it anywhere you would not use the indefinite in English.