This style of swimsuit can come in either one piece or two piece versions. The main difference between a Halterneck Bikini and a regular bikini is the top. Halter Bikini Tops tie around the neck as opposed to around the back. They are a bit more comfortable than regular bikini tops. Not too much of a change, but nice for those who want a bit more comfort.
Bandeau Top style swimwear is all the rage in designer swimwear circles. Bandeau swimsuits cover more of the bust than other bikini tops and they are strapless. So, bandeau swimwear is a great option for those who want to switch up their swimwear style while still maintaining a classic, somewhat conservative look.
If you want some really modest swimwear, then a Skirted Bathing Suit is a great option. As the name suggests, skirted swimwear covers more of the hips and thighs than a regular swimsuit. They can come in both one and two piece suits. Skirted swimsuits are for those who want to enjoy the beach or pool, while still being extremely modest.
A Tankini is a two-piece bathing suit. The bottom resembles your standard bikini bottom (although you can substitute whatever bottom you want) and the top resembles a one-piece bathing suit. Depending on the exact style you get, a tankini can range from being a piece of relatively modest swimwear to being a more revealing piece of swimwear.
Micro Bikinis are for those who want to really show off. As you can guess from the name, a micro bikini is incredibly revealing. The micro bikini top will essentially by a thin string, only big enough to cover the nipples. Likewise, the tiny bikini bottom will barely cover the genitals. Now, no laws ban them, but wearing a micro mini bikini might get you some bad looks depending on the area you live in, so make sure you put some thought into how others will react before buying. But, it is always good to have a mini micro bikini in reserve, in case you ever can wear it.
A String Bikini is a thin bikini bottom with only a string along the sides to keep it on. It is revealing, but not so revealing that you need to be afraid to wear it. Thus, a string bikini is a nice choice for those who want something that is both sexy and practical.