"This began with the National Bank Act of 1863 which required each bank to purchase a dollar amount of government bonds equal to one-third of its capital and surplus. [28] This collusion between bankers and politicians became more formalized with the establishment of the Federal Reserve System in 1913, …
You’re going to have to specify why that “didn’t help.” Since you said “securities” doesn’t “mean much to you in this context,” are you implying that you’re looking for a definition which clarifies things for you, in particular, at you particular level of understanding? If so, a little info on your background level of familiarity with such concepts would allow me to be more helpful.