Simple Analogy for Impedance and Load?
Effectively "impedance is resistance for AC waveforms". 


DC: R = Vdc / Idc
AC: Z = Vac / Iac  


"Load" is part of the system where target energy is dissipated and/or utilised. 
(Element in a heater, RF 'tank' in a radio transmitter, LED in a light, ...)



"Impedance" is the extent to which a "load" resists the flow of current when a sinewave at a given frequency and amplitude is is applied*. 

*That 'definition' is too tight but useful to start with - for ease of understanding and calculation use of a sinewave at one frequency and amplitude is simplest but in general terms it is the restistance to flow under the given conditions.

"Load" is simply the target which a specified waveform or output is applied to. Mechanically the "load" for a cyclist is arguably the bicycle as perceived at the rider contact points which the rider delivers energy into - ie pedals, handlebars, seat if seated and wind drag - but it is also a function of tyre resistance and gravitational load from rising (or falling) road level. 

Usually load is what is "seen" as an 'input' by the 'output' of some other system portion. eg a resistor is a load for a battery when battery potential is applied to it. A speaker is the load when audio from an ampliofier is applied to it. The speaker load consists of susbsystems where energy is dissipated but we usually don'tlook at these when considering the speaker as a whole. (eg air resistance from cone (the major component, hopefully), magnetic losses in core of speaker-driving inductor, copper (resistoive) losses in winding of coil and wiring, ... .