If you organize an event or activity, you make sure that the necessary arrangements are made.

If you organize something that someone wants or needs, you make sure that it is provided.

If you organize a set of things, you arrange them in an ordered way or give them a structure.

If you organize yourself, you plan your work and activities in an ordered, efficient way.

If someone organizes workers or if workers organize, they form a group or society such as a trade union in order to have more power.