In almost all cases, Access Time refers to that time a disk, an optical disk or an hard disk needed for reach or read a data sector.
There are a lot of factors that are involved in definition of access time. The physical speed of the hardware, the delay or the amount of time the hardware need for finding the data sector, the buffer and so on.
In everything that involves music production and also in the video production, lower access time numbers are better because a huge amount of data is needed to be reached fast.