Cannabis can be divided into different strains of the plant that in general offer different effects when used.  A strains can be seen as a particular variety of the plant type and different strains of the plant can come from different parts of the world.  There are two basic strains you may have heard of which are indica and sativa. There is now also a third strain called cannabis ruderalis that comes from Southern Russia. Plants from these basic strains can be cross germinated with each other for blended affect options, and from this we get hybrids.  Most cannabis at dispensaries is broken down into the two basic strains and many hybrid varieties which are identified by particular names.  You may also hear terms like “indica leaning” or “indica dominant” when there is more Indica in a particular strain than sativa. Indica variety cannabis originates from the Hindu Kush mountains of India and in general is said to offer a relaxing effect on the user. Sativa variety originates from  the East Asia steppes and in general is said to have a more energizing effect. Hybrid combinations of plants from these strains are bred to create specific effects for users that can be reliably expected (within reason) from a particular hybrid type. Names for plants and their hybrids can hint at effect reactions like ‘Blue Dream’ of ‘Purple Haze’.  Keep in mind that everyone is different and people can react differently to the same strain of cannabis.