Sativas, often referred to as "Daytime strains" have long leaves with thin long blades. The buds tend to be longer than their indica counterparts. Sativas often have lower levels of thc to cbd but a huge variability exists within either species.
Indica strains (often referred to as “night time strains” tend to grow short and bushy with wide leaves & short stubby blades. Indica strains usually have a higher THC content than Sativas.