MX is a type of switch, so from the name, I'm guessing it uses MX style switches (the most popular style of switch). Specifically MX describes the shape of the connectors on the switch. This means the keyboard will be compatible with aftermarket key caps, which are very popular.
EDIT: While the switches do look like MX switches to me, Logitech is also using MX as branding to describe mice, non-mech keyboards etc. This is confusing for someone who knows mechanical keyboards.
MX is a type of switch, so from the name, I'm guessing it uses MX style switches (the most popular style of switch). Specifically MX describes the shape of the connectors on the switch. This means the keyboard will be compatible with aftermarket key caps, which are very popular.
EDIT: While the switches do look like MX switches to me, Logitech is also using MX as branding to describe mice, non-mech keyboards etc. This is confusing for someone who knows mechanical keyboards.