In Mysticism, Mercury in Retrograde, which is when Mercury appears to move in reverse motion in the sky, occurs 3-4 times a year and lasts approximately 3 weeks each time.
A retrograde Mercury is believed to impact communication, travel, and technology, and to bring about miscommunications and delays.
During this time, it is a good idea to double check all your plans and be extra clear in your communication with others. Patience is key. Rather than starting any new projects, it may make more sense to use this time to revisit old projects, review prior plans, and focus on resolving any past misunderstandings.