introductory
Serving as the beginning or first, to help you start.
Introductory means serving as an introduction or beginning to something. An introductory chapter in a textbook explains basic concepts before diving into harder material. An introductory course in Spanish teaches you simple greetings and phrases before complex grammar. When a museum offers introductory classes on painting, they start with fundamental skills like mixing colors and holding a brush.
Introductory material prepares you for what comes next. A soccer coach might begin with introductory drills to teach basic ball control before moving on to complicated plays. A piano teacher starts students with introductory lessons on reading music and finding middle C.
Sometimes introductory also means special pricing or terms offered to new customers. A gym might have an introductory membership rate to encourage people to try it out. The idea is the same: making it easier for someone to begin something new.
Notice that introductory always points forward. It's the on-ramp, not the destination. Those first easy problems in your math homework are introductory because they prepare you for the challenging ones later.