SessLogs = log files of PowerCenter sessions; PowerCenter is the tool to perform masking tasks, sessions are individual load processes within workflows (process chains).
WorkflowLogs = log files of PowerCenter workflows (process chains); a workflow can consist of one or more sessions (I don't know how TDM 10.4.1 handles this topic, but probably at least one session is always contained within a workflow).
jobLogs = logs of IDQ (Informatica Data Quality) jobs; these probably often are profiling jobs for data analysis. The results of this data analysis are the data domains of the various attributes in source databases / files.
log_<n>.log = (if memory serves me right) log files of the so-called Service Manager of the software installation. Each installation is called a "node" within the Informatica domain, and the log files of each such node are stored within these directories.
Again, if memory serves me right.
tdm.log = probably (if memory serves me right) the log file of the TDM software itself; this software is used (via the web UI) to analyse data, to define and assign masking rules, to define, execute, and monitor masking and subset plans; and to maintain the test data warehouse(s).
Serialised workflows: no idea, it's too long ago since I've worked with the software for the last time.