Learn Turkish: Yolu tarif ediyorum. - I am describing the way.

Yol means "road" or "way". Because you are describing a specific way ("the" way) that receives the action of the verb, it takes the definite accusative case suffix -u, making it yolu.

Why are there two words, tarif and ediyorum, for "describing"?

In Turkish, many verbs are made by combining a noun with a helper verb like etmek (to do/make). Tarif means "description", so tarif etmek literally means "to make a description" or "to describe".

The helper verb is etmek. Why is it spelled with a "d" in ediyorum?

This is a spelling rule called consonant softening. When a few specific verbs ending in t, like etmek (to do) or gitmek (to go), get a suffix starting with a vowel like -iyor, the t changes to a d. So, et-iyor-um becomes ediyorum.

Where is the word for "I" (ben) in this sentence?

The "I" is already built into the verb! The personal suffix -um at the end of ediyorum tells us exactly who is doing the action. You could say Ben yolu tarif ediyorum, but Turkish speakers usually drop the Ben because it is already understood.