There is no standard transaction. The information is available for configurable time periods using transaction ST05N but it is not organized to readily provide a report of users and transactions. Also the information available summarizes a user's use of a transaction. There will be one entry (with count data) per user per time period. Daily, weekly and monthly summaries can be created and they are stored for configurable durations.
The information is summarized into a cluster table called MONI based on the STAT files that are written in the file system and regularly refreshed. MONI cannot be queried via SE16 etc., but SAP delivers a number of function modules that retrieve data from these tables.
It is also possible to configure audit logging via SM19 and read the log files via SM20. This will provide more detail but it also introduces new file management issues and requires a change to system settings.