A triphasic chart shows three levels of temperatures: pre-ovulation, post-ovulation, and then a second rise around 7-10 days after ovulation. Some women with charts that show this pattern turn out to be pregnant. But many do not. Likewise, your chart does not need to show this kind of pattern for you to be pregnant. Whether or not you are pregnant, progesterone, the hormone responsible for raising your temperature after ovulation, generally peaks in the middle of your luteal phase and this can cause this kind of pattern whether or not you are pregnant.
A triphasic chart can be promising, however, because progesterone levels generally increase after implantation (7-10 days past ovulation) in conception cycles, and sometimes this results in a triphasic pattern. If your chart shows a second significant thermal shift that begins 7-10 days past ovulation, Fertility Friend will indicate a triphasic pattern in the Pregnancy Monitor. A triphasic chart, however, is not a definite sign that you are or are not pregnant. It is just increasing your probability if you also have well-timed intercourse. Likewise, you can be pregnant and not have a triphasic pattern. Like all signs of possible implantation or pregnancy, you can really only speculate about it once a pregnancy has already been confirmed.
For a detailed statistical study, please read FertilityFriend.com's Triphasic Pattern and Pregnancy report.