What establish a session?

As an analyst I'm running multiple queries on our Oracle ERP via Power Query (Power BI). Now, I hit some form of session limit on my default profile's session limit. How do you evaluate how many sessions I use without accessing the Oracle database directly? Are they the number of tables you access in the FROM statements? Error message: >OLE DB or ODBC error: [DataSource.Error] Oracle: ORA-02391: exceeded simultaneous SESSIONS_PER_USER limit.