For small power inverters most any battery is fine. For higher power, from around 500 Watts and up, you’re best to use an inverter battery. An inverter battery is also known as a deep cycle battery. It is designed to deliver higher current continuously. A typical automobile battery for example is made for a blast of very high current for a short time, starting the engine. But for use on an inverter you need a steady flow of current for a much longer period of time. And as an opposite it won’t deliver a high boost of current for hard engine starting in extreme cold for example like the other battery.
They could be sealed or not. That depends entirely on the design and type. Lead-acid types are often not sealed. Gel-cell and similar compositions are often sealed.
