Sensimilia simply means the plant has no seeds. It is this kind of plants you will want to grow.
When plants do not contain any seeds, they are able to use a lot more energy to produce cannabinoids. If the female plant does start to build seeds (when it is pollinated by the pollen of the male plants), resin production will lower. That is why males have to be taken away as soon as possible.
Under special conditions, some plants can also become hermaphrodite (= they become female and male at the same time) and start to produce seeds. This is bad news for the plant's THC production, which will lower. Moreover, these seeds are usually not good enough to grow new plants.
If you want high quality buds, you will need to use sensimilia plants. They have a great taste, aroma and produce a good amount of cannabinoids.