How does article i, section 6 of the constitution protect members of congress?

Members of congress are to be paid for their work from the U.S. Treasury. Amendment XXVII prohibits members from raising their salaries in the current session, so congressional votes on pay increases do not take effect until the next session of congress. Article I, Section 6 protects legislators from arrests in civil lawsuits while they are in session, but they could be arrested in criminal matters. 

I no speak eapanol lllppp