Portable fans move air around the room to create a cooling effect when there's no AC. At the low end, you could get a tiny desktop fan for individual cooling. At the other end of the spectrum is a giant pedestal fan that oscillates at high velocity to cool whole rooms. Between those extremes are sundry designs that vary in function. A personal fan placed next to your arm chair may be all you want. Cooling your bedroom needs a different approach. Here you could use a larger tabletop fan with more speed options. A turbo floor fan or a tower fan could be a better choice.
One of the best things about portable fans is, of course, their portability. You can move them around your home wherever they're needed. In a workshop, you can mount a portable fan on the wall. Convenient hooks allow you to move it around the space. Battery-operated fans are available when electric power is absent. Portable rechargeable fans offer added convenience. At the top end of the portable fan market are models that use Air Multiplier technology. These create powerful air streams with almost no noise.