With all of my effects, I've been running through the clean channel of my combo amp. What does the insert effects loop jack do? Does plugging in a pedal disable the preamp of combo?

Is there any way to disable the amp's preamp, and use, say my Digitech effects board as my preamp? Any advice and info is appreciated. Thanks!

Some amps have an effects loop.

If theres an effect in and out. You can plug your guitar in the regular jack and have the effects unit plugged in using the effects in and out. If there is only the one effects port then i would imagine you have to go Guitar > Effects > Amp

and therefore not be able to switch to the amps other channels.

If its a good amp there should be an effects loop that you can switch to as well as other channels on the amp. Thus creating another channel.

My Peavey JSX for example has three footswitchable channels, as well as a footswitchable Effects loop allowing me to use all of the amps features as well as any outboard unit at the press of the footswitch

i thought effects loops only worked well with stomp box chains.

oh, and a lot of heads allow you to bypass their preamp sections, but i don't know how common the option is in combo amps. i guess it depends on what kind of amp you have...?