Activators belong to the category of drugs. In pharmacology, activators should be called "agonists". Exciton is generally a receptor, which binds to the receptor and produces biological effects by exciting or activating the receptor. Excitators can be classified in many ways:

According to the receptor types, it can be divided into: (1) agonists of enzymes, (2) agonists of neurotransmitters and (3) agonists of hormone receptors.

According to the action intensity, it can be divided into (1) complete agonists and (2) partial agonists.

Depending on the structural type of the agonist, even more. For example, agonists of adrenergic receptors include catecholamine and choline of acetylcholine receptors.

Generally speaking, the action principle of agonists is that the activity of receptors changes after binding with them. If the receptor is an enzyme, the activity of the enzyme will be enhanced. If the receptor is a receptor on the synaptic membrane, the combination of agonist and receptor will affect the transmission of nerve signals, which may activate or inhibit conduction, depending on the type and location of agonist and receptor.

The biological effect of complete agonist binding to receptor increases with the increase of agonist concentration, while some agonists often have inhibitory effect at low concentration and excitatory effect at a certain concentration.

In the principle of action, the intensity of excitement is often related to the binding and dissociation rate of agonist and receptor. There are three concepts: receptor affinity, intrinsic activity and dissociation rate. An efficient agonist needs to meet three conditions: high affinity, high intrinsic activity and high dissociation rate.

In a word, your topic is too big. You need a book if you tell all this knowledge. I suggest you take a look at the part of pharmacology about nervous system drugs and hormones, and the principle of action of enzymes.