Someone explain the effect "Resolution Scale"?

Upscaling takes a smaller image resolution and converts it to a higher resolution.(i,e, 1920x1080 scaled up to 2560x1440)
Downscaling takes a larger image resolution and converts it to a lower resolution. (i.e. 2560x1440 scaled down to 1920x1080)

becuz on edges textures is seratted, i play in 1080p e use the value "1".

Then your image is scaled 1:1 or 1080p. The edge serration is probably due to a lack of anti-aliasing of some sort.

Have you ever watched an old VHS tape on an HD television? The resolution of the TV is 1920×1080, but the resolution of the VHS is 576×240. So, to be able to watch it full-screen, the image is upscaled, magnified.

Same principle in video games: you make the video game run in, for example, 720p, but you upscale the final image to 1080p on you monitor. This helps weaker video cards, since they only have to render the game's 3D models and world in a much smaller resolution (requiring a lot less processing power and resulting in higher frame rates), but you still see an 1080p image. The result is usually a little blocky, but there are tricks to hide it.
This is, by the way, how most console games work: they actually are played in 540p or 720p, and the image itself is just upscaled on the television. This is why so many console games have motion blur, it is the easiest trick to mask upscaling.

On PC, you can do the opposite: render the game on a resolution your monitor cannot display. For example, you have an ancient game like Deus Ex 1 from 1999. You enable high resolutions on your GPU and make the game be rendered at 3840×2160. You monitor cannot handle it, so the final image is downscaled to 1920×1080. The reason this is good is that the resulting image is much clearer, sharper than using anti-aliasing, or in some cases (for example with a strategy game) you see more of the gameplay field.

Your 1:1 means you render the game in 1080p and it is displayed in 1080p, so it is not upscaled or downscaled: you see it as it is, without any video magnifying tricks.

Upscaling/downscaling can have certain benefits. For example, upscaling a resolution smaller than your native resolution can allow menus that are small at native resolution to be easier to read. On the flip side, by my experiences, sometimes upscaling/downscaling can cause fragmentation or grainyness. It can also cause awkward stretching if you're trying to scale to a different ratio'd resolution (much like trying to watch a full-screen/wide-screen movie stretched into the other format).

Generally, I'd say avoid it using it unless you've got something specific in mind (such as reducing graphic demands or adjusting menu sizes), or the game doesn't support higher resolutions by default.
As noted above, Anti-aliasing is usually your best bet in removing awkward edging on textures.

This Resident Evil 7 Graphics Optimization Guide may be a useful reference: https://savegamelocation.com/resident-evil-7-graphics-optimization-guide/