This site has a good explanation of sovereign citizenship. Specifically:
In the 18th-century colonies, nouns were usually capitalized, although the practice was going out of style by the time of the Revolution. Based on that, sovereigns see secret meaning in the use or non-use of capitalized letters. For example, a "citizen" is a sovereign citizen imbued with all natural rights, whereas a "Citizen" is a 14th Amendment citizen subject to the rules and regulations of government.
While that is specifically American in context, I think the principle is the same. It's basically a kind of numerology but with the conventions of written language.
Speaking of numerology, I can't wait for them to discover that, in ASCII, adding or subtracting the value of a [space] (decimal 32) converts between upper- and lowercase. (A=65, a=97; B=66, b=98...). Surely that gives the [space] a special magic, but is it good magic or bad magic or can anyone use it? And the fact that lowercase uses bigger numbers than uppercase must also carry some significance, right?
For a fun time, use the phrase "sovereign citizen capital letters" in a web search.
Wikipedia has a pretty good article.
To summarize, "humanism" is an umbrella term that includes many different philosophies that share the common idea of promoting the well-being of people during life. There are religious humanists from different faith communities (and Religious Humanists, a specific community of early 20th century naturalists who treated their humanism as a religion), Marxist Humanists, etc, but right now, "humanism" and "secular humanism" can be treated as synonyms.