Mercury retrograde is an optical effect: from Earth, the planet seems to reverse through the sky for about three weeks. Astrologically, it is linked to communication, travel and technology, the things Mercury rules.
The re- words
It is a good time to revise, reconnect, review and repair. It is a harder time to launch, sign or buy without reading the details twice.
A practical approach
Back up your files, confirm your plans and give people the benefit of the doubt when messages go astray.