The parameter to the $ function isn't just the name of an element. Instead, it's a Cascading Style Sheets selector, and as such can be a style class name, an element type or an element name. In CSS, element names are prepended with a pound sign. Since I'm looking for the element named mydiv1, I pass #mydiv1 to the function.
The function doesn't return an HTML object but rather a jQuery object that serves as a proxy to my HTML element. This object includes a method called html() that either returns the inner HTML of the element (when you pass no parameters) or sets the contents (when you pass a string as a parameter). I wanted to set the contents, so I passed a string consisting of the value of the text element. Obtaining the text element's value works similarly, except I called val() instead of html(), and since I wanted to read the value, I passed no parameters.
Easy enough. But when I typed this into Visual Studio, IntelliSense went to work and then understood jQuery. When I type $, a popup appears listing commands, and that one is first. But the whole command is a single character, so I just continued. I typed an open parentheses, and an expanded IntelliSense message displayed.
This message told me the name of the function and the parameters, and additionally described each parameter for me; the message changed as I typed each next parameter. That's just like coding in C#.