This is the series of blocks Amino acid substitution matrices (BLOSUM), all of which are derived based on direct on direct observation for every possible amino acid substitution in multiple sequence alignments.
A volt-ampere (VA) is the unit used for the apparent power in an electrical circuit, equal to the product of root-mean-square (RMS) voltage and RMS current.[1] In direct current (DC) circuits, this product is equal to the real power (active power) [2] in watts.
Study electronics. Seriously. A DSO is an incredibly complex piece of electronics, combining both highly advanced analog and highly advanced digital techniques at every step. I can't possibly tell you all you need to know in a Quora answer. And you ask the question as if from the perspective of someone who knows nothing of electronics.