What does 'outlook ... VFR' mean?
Outlook VFR is usually found in the so called "Area Forecast". It is the last part of the portion which describes clouds and weather, which could affect VFR operations. 

The area forecast for every region is valid for 12 hours, followed by a 6 hour categorical outlook. 

There are three types of outlooks, VFR, IFR and MVFR (marginal VFR). As mentioned in Jeppesen's Guided Flight Discovery Instrument/Commercial Manual:


  A ceiling less than 1,000 feet and/or visibility less then 3 miles is
  considered IFR. Marginal VFR areas are those with ceilings from 1,000
  to 3,000 feet and/or visibility between 3 and 5 miles.


Everything "better" (as in higher ceiling and/or visibility) is considered VFR.

Here is an extract from an Area Forecast:

CLDS/WX VALID UNTIL 062100...OTLK VALID 062100-070300
[...]
NRN PEN...BKN010-020 TOP 100. OCNL VIS 3SM BR. BECMG 1214 BKN025
TOP 120. ISOL -SHRA. 18Z BKN040 TOP FL220. WDLY SCT -SHRA/TSRA.
CB TOP FL420. OTLK...VFR TIL 02Z SHRA TSRA.


The first part is an extract from the Heading Section. here you find the time for which the Clouds and Weather part as well as the Outlook part is valid.
The second part consist of the mentioned Clouds and Weather as well as the Outlook. I'm not going to decipher the whole thing now, but here is a short explanation: 

You can see the more detailed forecast, valid from the time of loading the Area Forecast to 062100, which means the 6th of the month, 21:00 Zulu time. After that, from 062100-070300 so from the 6th at 21:00 Zulu until the 7th at 03:00 Zulu, the outlook is what counts. In this case it is VFR until the 7th of the month at 02:00 Zulu, where showers and thunderstorms (in connection with rain) are expected.

Conclusion: The outlook gives a general idea what the weather will be like up to 6 hours after the forecast part of the Are Forecast. This can help in flight planning. 

For more information about VFR refer to DannyBeckett's detailed answer.