Simply put, CO2 sequestration is the isolation of anthropogenically produces CO2 from the atmosphere. There are various types of CO2 sequestration such as mineral carbonation, storage in geological formations, biological sequestration, and oceanographic sequestration just to name a few. Our focus is on CO2 sequestration via mineral carbonation. More detailed explanations of other methods can be found in the links section.
Mineral carbonation is the only permanent (on human timescale) method of sequestering CO2. This is because CO2 is reacted with a suitable metallic cation which chemically binds the CO2 into a stable carbonate mineral form. Mg2+ is by far the most abundant cation. Serpentine group minerals are the most abundant and widespread source of Mg2+, with accessible deposits being able to sequester the CO2 that would be released from all known fossil fuel reserves.