The random speeds are 4k read/write speeds. The time it takes for the drive to read/write a 4k file (the smallest the drive supports).
HDDs are notoriously slow at this. A 7200 RPM drive usually averages about 0.75 - 1.5 MB/s. A 5400 RPM drive about 0.5 - 1 MB/s. Slower if the file being read/written happens to be in a bad spot (has to wait for a full platter rotation instead of a partial rotation).
This is the reason SSDs are so much faster than HDDs. It's not the sequential speeds everyone looks at, which are only about 4x faster for a SATA SSD. It's the random read/write speeds, which are about 30-50x faster with a queue depth of 1, and hundreds of times faster with a deeper queue depth. If you're unhappy with the storage speed of your laptop, the best thing you can do is upgrade the HDD to a SSD.