Transiting Exoplanet Survey Satellite (TESS) is a satellite project aimed at surveying 2,000,000 nearby stars for Transiting Planets. It would use four wide-angle telescopes and store three months' data, allowing it to send down only promising examples. It aims at stars brighter than 12 Magnitudes, G-Type Stars and K-Type Stars, as well as nearby M Dwarves, small M-Type Stars.
TOI stands for Tess Object Of Interest, a term for a possible planet, i.e., the location of observations that appear to reveal a transiting planet. TFOP (for Tess Follow-up Observation Program) is an initiative to investigate TESS discoveries, e.g., whether to confirm a TOI as a planet.
As of November 2017, announced plans are to launch in March 2018.