Critical. A vulnerability whose exploitation could allow code execution without user interaction. These scenarios include self-propagating malware (e.g. network worms), or unavoidable common use scenarios where code execution occurs without warnings or prompts. This could mean browsing to a web page or opening email.
A strain is a stretching or tearing of muscle or tendon. A tendon is a fibrous cord of tissue that connects muscles to bones. Strains often occur in the lower back and in the hamstring muscle in the back of your thigh. Initial treatment for both sprains and strains includes rest, ice, compression and elevation.
Strain = A change in shape or volume in response to a stress. Stress is the cause, strain is the effect! There are three types of stress: 1) Compressive stress  Forces that squeeze or push toward one another from opposite directions (cause shortening or flattening). 2) Tensional stress  Forces that pull away from one another in opposite directions (cause stretching or extension). 3) Shear stress  Forces that are offset from one another and operate in opposite directions (cause a shear strain). The behavior of rock during stress depends on: 1) The type of rock. 2) The type and amount of stress.