WiFi relay - what to choose?

Question

WiFi

Hello.
WiFi does not cover the entire apartment, it is necessary to fix this error with a little blood. "Long" antennas did not help, too many concrete walls. You can’t move the router (there are no sockets in “good” places, and some wires are laid). It is impossible to lay new wires (otherwise I would buy a cheap radio station, but that's the end of it). Nothing is required - neither fast Internet (even 50 kB / s in a “deaf” room is normal), nor a local network (they are such computer scientists that it’s easier for them with a flash drive). The Internet has asked more questions than it has answered - for example, searching for “WiFi bridge” leads to advertisements for specific devices (SEO in action!) and articles from the WiFi.b era about connecting factory management with the shop floor (and this is clearly not mine).
Most of the clients (a couple of netbooks and an ancient smartphone) use WiFi.g, but the main router (D-Link DIR-615) has 150 Mbit WiFi.n. Therefore questions.
1. What is the difference between bridge, repeater and WDS?
2. What features to pursue?
3. What are the pitfalls?
4. What kind of equipment can you recommend as good?

Answer 1

I solved a similar problem with the Chinese craft comfast CF-WR500N, the most easy-to-use device requires only an outlet.