In tomato variety shopping, one will want to consider plant growth type. Determinate means the plant is a determined (generally more compact) size, versus indeterminate, which keep on growing stems off the main stem which all continue growing as well. The stem of indeterminates never ends in a group of flowers like determinate varieties, the flowers grow as offshoots from the stem rather than at the end so it continues producing over a prolonged period more so than determinate varieties. Indeterminate varieties are also often staked and pruned to make efficient use of vertical space.
Some subsequent considerations might be fruit size, usage, taste, colour of fruits, maturity time, or where it was bred in terms of the conditions it was meant to grow in. There are so many tomato varieties in the world, some with striking differences, others with subtle differences, enjoy exploring the diverse and tasty world of tomatoes!