It's kind of a complicated answer, so here goes: LATCH stands for Lower Anchors and Tethers for CHildren, and refers to both the lower LATCH anchors in the crease of the vehicle seat, and to the top tether anchors usually located behind or above the vehicle seat.
Vehicles made after Sept. 1, 1999 for the 2000 model year for sale in the U.S. were required to have top tether anchors, and older models can usually have top tethers retrofitted.
Vehicles built after Sept. 1, 2002, when the federal requirement for lower LATCH anchors went into effect for the 2003 model year in the U.S. market, have a minimum of two sets of lower LATCH anchors. With the exception of some VW and Audi models, lower LATCH anchors cannot be retrofitted. Some pre-2003 model year vehicles may also have lower LATCH anchors because some manufacturers included them before the requirement went into effect.
Vehicles weighing over 8,500 lbs. (like the Ford Excursion and F350 pickup) are exempt from the federal requirements for LATCH, although I believe the Excursion does have top tether anchors. Also, convertible car models are not required to have top tether anchors.
Hope this helps.