As per common market research pure brand recall requires "unaided recall". Unaided recall means that no help or aid is given to consumer to recall the brand. It was already in the mind of the consumer under a product category. For example when a respondent is asked to recall the names of any phone brands he may know, or any beer brands he may know & the brands which he is able to recall without any help will come under unaided recall.
The other one is "Aided recall" which tells you the level to which a brand name is recognized when the actual brand name is prompted. An example of such a question is "Are you aware of "Apple" brand?" In this case the Brand name is told to the respondent.
To increase their brand exposure, companies want their brand to come under unaided recall in relation to their competitors. The first brand name which is recalled (often known as "top of mind") has a distinct advantage in brand space over others competitors, as it has the first chance of evaluation for purchase by the consumer.