SVG profiles are subsets of SVG specification. It is usually because limitations of target devices where the SVG is used.
For mobile devices there are following profiles:
SVG Tiny does not support gradients, transparency, clipping, masks,
symbols,or SVG filter effects.
SVG Tiny 1.1 Plus includes the ability to display gradients and
transparency, but does not support clipping, masks, symbols, or SVG filter
effects.
SVG Basic does not support nonrectangular clipping or some SVG filter
effects.
External links:
http://www.w3.org/TR/SVGMobile/ -- Difference between SVGT and SVGB
http://wiki.svg.org/index.php?title=SVG_Tiny_1.1_Plus -- Differences among SVGT profiles