The read speed is how long it takes to read something from the drive -- so, how long it takes to open a file that’s stored on the drive.
The write speed is how long it takes to save something on to the drive.
Read and write speeds are typically recorded with the letters “ps” at the end of the measurement. For example, a drive that has a write speed of 32MBps means that it can record 32MB (megabytes) of data per second.
There are various sites on the web that allow you test read and write speeds, as well as sites that help you convert various measurements.