The suffix -ment attaches to verbs to create nouns that describe either the action of doing something or the result of that action. When you add -ment to a verb, you transform it into a thing you can talk about.

Take the verb enjoy: add -ment and you get enjoyment, the feeling or state of enjoying something. Move becomes movement, the act of moving. Govern becomes government, the system that governs. Achieve becomes achievement, something you've achieved.

Sometimes the noun describes the process itself: development is the ongoing process of developing. Other times it describes the outcome: an agreement is what you have after people agree. And occasionally it describes both: treatment can mean the act of treating someone (medical treatment in progress) or the specific care they receive (a new treatment for an illness).

You'll find -ment everywhere in English because it's such a useful tool for turning actions into ideas we can discuss. Instead of saying “the fact that we improved,” you can simply say “the improvement.” Instead of “when things get excited,” you can say “the excitement.” This suffix helps us package experiences, processes, and results into words we can examine, compare, and understand.