apex – Governance Limit per Transaction : How is it counted ? 101 SOQL executed Error

I have an LWC (which performs searches and allows a User to move records between 2 Master records). When User clicks on Finish button on LWC, then

1. it calls an Aura Enabled Apex method (identifyA),and decides what needs to be done as part of movement of slave record(s) between the 2 Master records, and it creates a record of these movements in a custom object (customObj1)
2. There is a trigger written on the customObj1, which actually carries out the actualy movement that was identified in above step.

Problem: I keep hitting governance limit 101 SOQL executed.

1. What I need to understand is when does the transaction begins ? (so that I can understand from logs which queries are getting considered which causes 101 governance error)
   1.1) Is it when I click Finish button and once a request goes to the server to execite apex server side code ?
   1.2) Is it after I insert a new record and after that point all SOQLs are considered ?
2. OR does this transaction also considers all the SOQL fired under method identifyA as well ?

Basically, when does Apex consider a transaction has begun and it starts to count of SOQL executed ?

Also I added in my code to print in the log the current query count, and there it says it has a limit of 300, why and how is that ?

Please let me know in case there are queries and I will answer them.