Here is my 2 cents:

EC (Everpresent Carry) = immediate functionality; designed to make general tasks easier, regardless of situation. Everybody has his/her own preferences here, but generally include things like keys, wallet, LED (light emitting diode) light, lighter, multi-tool, cellphone, etc. Think what makes my life easier.

PSK (Personal Survival Kit [up to 72 hours]) = immediate first aid + immediate subsistence; designed to maximally increase the likelihood of surviving current situation. PSK's are generally designed for survival at a fixed location until rescued, which most typically takes place within 72 hours if you did your pre-trip work and/or are carrying a PLB (personal locator beacon), or other viable communication device. Every member of your party should be carrying one. There is much controversy concerning these, and they take on an endless variety of shapes, sizes, and configurations, not to mention the endless content debates. Just think worst case scenario and common sense.

BOB (Bug-Out-Bag [72 hours to 2 weeks]) = longer term first aid + longer term subsistence; designed for evacuation either to or from home. BOB's are generally designed to facilitate fast and constant movement over an already established route. Every member of your party should carry his/her own. These will vary depending on distance to be traveled, seasonal weather, and generally will not focus on food aqcuisition, etc. These can and should be supplemented during the bug-out with predetermined caches along the route. Get the whole family involved in preparing for this one, as it is much more than just a kit.

EK (Expedition Kit [2 weeks to indefinite]) = civilization is not a foreseeable option gear; designed for complete self-sufficiency. EK's are generally designed to enable one or more individuals to live off the land for extended periods of time. Much of this kit can be shared between party members, such as hunting rifle, camp axe, rope, etc.

That was fun!