There are several types of tonneau covers on the Tacoma market today.
Roll up covers: These are low-profile systems that sit flush with the top of the bed, making for a very streamlined appearance. Typically made from heavy duty vinyl, roll up covers unfurl from the back of the cab, along the bed rails, and latch in place at the tailgate. They offer good weather protection; however, are not heavy duty in the sense you can place large objects on top of them as they typically lack any significant structural framing. That said, there is a new type of roll up cover that is beginning to catch on. This second version is made from narrow metal slats (usually aluminum) that unwind out of a drum to lay flat across the bed of the Tacoma. Also weatherproof, these metal-based versions are significantly stronger and more secure but come at a higher price point (some of these models are also electrically controlled).
Fold up covers: This type of cover is the most prominent on the market as it is highly affordable and offers an excellent blend of weather and cargo protection. Folding covers typically come in two flavors: bi-fold and tri-fold. The former folds from the middle, creating two equal compartments to either side of the center line. The latter, a tri-fold, sees a similar tonneau cover sectioned into three areas which makes partial bed access easier as you can only lift the third section, for example, if you wish to only access the tailgate area. Folding covers are fairly sturdy as they use an underlying metal frame to keep the vinyl on top properly tensioned.
Lift-up or hinged covers: The final type of Tacoma bed cover is one that has been on the market for the longest time and could be considered the forefather of tonneau covers. This last option is a one-piece tonneau cover that lifts up from one end, typically using a gas-assist strut, but remains fixed at the other end (usually fixed at the cab end). These solid, strut-lifted covers are made from fiberglass or plastic and are often a dealer option that comes painted to match the exterior color of the Tacoma. Certainly less prevalent due to their size and weight, nonetheless these original style tonneau covers are still widely available and offer excellent cargo security and protection from the weather. Like the other systems, a solid lifting cover (model dependent) can also integrate with the locking tailgate.