There are two main types of feeders for hummingbirds and these are inverted or saucer designs. Hummingbird feeders hold sugar water and so are a bit different from seed feeders. The inverted feeders have a tank to hold the sugar water that rests above the part with the little feeding holes. These are two-part feeders. The sugar water is poured into the small tank and the bottom portion with the feeder holes is then screwed onto this. Once the two parts are secured together, the whole thing is turned over and hung outside. These can hold more than saucer feeders but some that are poorly designed or constructed and may drip and leak. Saucer feeders are just one piece and the feeder holes are at the top of a spaceship looking saucer where the sugar water is accessed. These hold less and may not be as noticeable to birds but generally don't leak. Some hummingbird feeders are designed with small perches at the feeder holes, while others are not.
Cylinder or Tube Seed Feeders
These feeders are for small to medium perching birds that eat seeds; they are generally top loading. Some are designed as one tall, slender cylinder with up to 20 feeding holes and perches while some are built with three cylinders in one, such as the Opus Top Flight Copper Triple Tube Bird Feeder, which has three feeder tubes each with four feeding holes and perches. This type can be useful for attracting a variety of birds, as each tube may be filled with a different type of seed: thistle, sunflower seed and cracked corn, for example. Many tube feeders are made with plastic and metal with specific feeder holes, but some are made of wire mesh to be used with larger seeds or kernels (thistle doesn't work with these), and the birds can feed from any side and any level on the tube.
Suet and Seed Cake Feeders
Some are more decorative than others, but the most simple suet cake feeders are constructed of a vinyl-coated metal cage that opens to house the square block of hard suet cake. The birds can grasp onto any of part of the cage and poke their beaks through to eat. These are made with a large U-bend hook and are great for sliding right onto a slender tree branch or any other hook near porch or patio. Placing several of these around the yard can make room for more species at once. If there is just one main feeder, then all the birds will generally try to fight over it. Placing a few of these suet cakes around eases the competition.
Platform and Tray Feeders
Essentially, these are any feeders that provide a tray or platform to set seed and bird food on. Some are simply just a hanging tray and that's it; others are built with a dome shelter above or may be as elaborate as a finely carved gazebo or open mini house for the birds to fly into and eat. Many of these will not deter squirrels in the least, since they can simply climb right up and help themselves. Some of the plastic dome feeders, however, are deemed squirrel-proof and can also keep out large birds, depending on how low you adjust the dome over the seed reservoir.