Think of it this way.
You have a channel, i.e. single track. On that channel if you have EQ controls it is the same as having an EQ insert. You "insert" the effect into that channel to affect the whole signal.
Typically you would insert a compressor into the channel to affect the whole signal.
With a send, you "send" the signal to a buss seperate from the channel. That bus is usually known as an aux. There you place an effect, such as reverb or delay and mix the aux with the original channel.
Sometimes you may want to use things like EQ and compression as effects so you "send" the channel signal to the aux where a EQ or compressor is added. Then you mix the un-affected channel with the EQ'd or compressored aux bus.
EQ and compression are sometimes thought of as processors, because you insert it into the channel and "process" the whole signal. While reverb, delay, chorus, etc are thought of as effects and you use part of the "affected" signal to mix back in with the original.