$L(M)$ is used to denote the language that is recognised by the Turing Machine.
For an encoding, the general notation used is $<M>$.
The encoding of a TM, is a string that encompasses all the information of the 7-tuple describing $M$. You can think of it as "writing the 7-tuple as a binary string" (but this is a simplification). So the encoding of $M$, is just a string that describes how the TM works.
Thank you so much Arjun Sir!