Welcome to the forum.
UHS-1 is a higher writing speed than a "reguilar" SD card. The manual says you can use a UHS-1 card, but you you won't get the benefit of the speed. Any SDXC card from Amazon, Best Buy or Staples, etc. will be fine.
You would still be able to use a SDXC UHS-I (Ultra High Speed One) card. Here's a photo of a fairly recent SD card I have from SanDisk. There are several markings:
170 MB/s (the theoretical maximum read speed). One often has to dig to find things like sustained read or sustained write. That's perhaps the most import to understand; especially if working with video.
SDXC (SD eXtended Capacity). There is also SDHC (High Capacity) as well as the much older plain vanilla SD.
The "3" framed by a "U" indicates the write speed.
The 10 framed by a "C" indicates the speed class which represents the minimum speed.
Then the newer V30 indicates the Video speed. This typically represents the sustained write speed.
I just wish they got rid of all this garbage and simply put the sustained write and sustained read figures.
Back to your specific case... A card such as this one. Or an SDHC card will be a-ok in your Rebel T7. Do stick with reputable* brands though.
* While I have always ever used SanDisk cards myself, I'm a bit annoyed now at their newer offerings. e.g. they have one advertized as 300 MB/s. Yet they omitted the "V" rating on it! Come to find out, it's only V30. So while the theoretical read speed is faster, offering say faster transfer to your computer (assuming how you are connecting isn't the bottleneck), the sustained write is still only at 30 MB/s (V30). Guess they were ashamed of putting that V30 designation on the card. That's getting to be quite shady in my eyes.
