I'm not quite sure what your question is, but I'll take a stab at it.
The "insert" on the channel strip is both a send and return. An "insert" patch cable has a Tip/Ring/Sleeve (TRS) connector on one end and 2 regular mono 1/4" jacks on the end. The signal comes out of the mixer (usually) on the tip of the TRS connector, to the mono 1/4" plug labeled tip, which is the input to your effects unit. The other mono 1/4" plug labeled ring plugs into the output jack your effects unit, and returns to the mixer channel strip via the "ring" segment of the TRS connector, thereby adding the effect to that channel strip only.
If you look closely to a TRS connector, you will see that there are three separate portions of the connector...Tip, Ring and Sleeve...in a stack. On a mono connector, there is just the Tip and the Sleeve.
I hope this answers your question, or at least helps...