INSRIS will be insulation resistance. Approximately 500VDS is applied between L/N and E and the current measured. For Class I (earthed) appliances, this should be greater than 1MOhm, though anything below about 5MOhm should be looked into. A lot of appliances will get values in the range of hundreds of MOhm, and I think the tester used in your printout must not read higher than 299MOhm.
VIS is visual inspection.
DI is double insulated, i.e. class II - no earth bond or insulation resistance test to carry out.
L VOLTAGE is low voltage i.e. class III - no earth bond or insulation resistance test to carry out.
I'm not familiar with the specific software or tester used for this printout, but most of the testers will log data and this can be then put into a report.
As stated in another answer, a lot of PAT testing companies just say 12 months between combined inspection and testing. In an office environment (warning PDF), stationary equipment can go 4 years without testing, but hand-held equipment needs testing every year. Visual inspections need to be carried out more frequently. It gets complex when you have a lot of things that need testing and bring new devices onsite.
It is really important to note that these are only guidelines though. As far as I know, there is no law requiring PAT testing, just that you maintain safe electrical equipment.
In a small company I used to work fosense sent two people on a 1 day training course at about £120 each. This paid for itself in a year.