When you use the causative form of a verb, you can describe who makes someone do something, and who lets someone do something.
Forming causative verbs:
ru-verbs: Drop the -ru and add -sase-ru
食べる -> 食べさせる
u-verbs: Drop the -u and add -ase-ru.
はなす -> はなさせる
する -> させる
くる -> こさせる
The basic strusture of a causative sentence is as follows:
(dirctor)は (cast)に (action).
The professor made the students memorize the dialogue.
The director decides what is allowed and what is to be done. Marked with は or が.
The cast preforms the action. Usually goes with に.
The action is described with a causative form of a verb.
There are two meanings of the causative form. Any causative verb can be interpreted either as "make sombody do" or "let somebody do". Context can be used to determine which meaning is correct.
If the helping verb てあげる, てくれる or てもらう follows a causative verb, you can assume in almost all cases that it is a "let" causative verb.