Changing US Light Switch

[IVIaGiC]

I live in a 50 year old home in the United States. An outside flood light recently started acting up, only turning on after flipping the switch for awhile. I opened up the cover and there seems to be 2 seperate white wires attached to one side of the switch(both on the same screw) and a single black wire on the opposite sides screw. This switch is next to 2 others, one controlling another outdoor light, and the other controlling a porch florescent light. Both outdoor light switches have the same setup, with one black on its own screw and 2 separate white wires both connected to the other screw on the switch. However, the florescent seems to have 2 separate whites(again connected on a single screw) and a red wire connecting to the other screw on that switch, with no black wire. What type of switch would I need for this? In my very limited experience with wires i've never came in contact with a setup like this.