You've heard the rhyme, "Leaflets three, let it be"? It's a rhyme to help you remember what poison ivy plant looks like. You will also hear the version, "Leaves of three, let it be." It means the same thing, but some sticklers prefer to refer to the individual parts of a compound leaf as "leaflets," while the less pedantic simply call them "leaves."
Regardless of which version of the rhyme you like better, as you can see from this picture of poison ivy leaflets, the plant clearly does have leaflets or leaves of three parts. Knowing about the tripartite nature of poison ivy's foliage is a first step in identifying this rash-causing menace and keeping clear of it, so as to avoid coming down with the rash, in the first place, and thereby obviating the need for treatment of poison ivy rash. But other types of plants also have "leaves of three." So knowledge of this feature will get you only so far in truly being able to tell poison ivy from other plants.
The next step for those interested in being able to differentiate this weed from vines that look like poison ivy is to study my poison ivy pictures, which show you what the plants look like at different times of the year (and, consequently, at different stages of growth).