A family of Microsoft word processing software products for creating web, email, and print documents.
For future reference, the "space at the end of the first part of the line" could have been a paragraph mark, which stores paragraph properties such as line spacing, and these properties will affect the whole text paragraph. If there is also a space character, for example at the end of the text line, any overrides to the font size (for example) may also change the line spacing (for that whole line of text).
You can click the ¶ icon on the Home tab to show/hide nonprinting characters in the document. Pilcrows, ¶, represent paragraph marks, while dots represent ordinary spaces (degree signs represents nonbreaking spaces). See the screen shot below.