A paragraph break (hit Enter or Return on the keyboard) is always more meaningful than a line break (hit Shift + Enter or Return on the keyboard).  A paragraph break inserts what looks like a double-space in between one line of text and another, and allows screen reader users to parse the information on the page more readily.

Although programs like Microsoft Word have options to create single-spaced documents with paragraph breaks, web pages do not.  You may find using a line break more esthetically pleasing than a paragraph break, but line breaks can create problems for screen reader users.

While a screen reader can interpret a paragraph break as "blank," a line break may not be indicated to the user.  The text on the new line may sound like a new sentence, instead of the start of a new paragraph.

Everybody experiences the world, including content they access on the internet, in their own way.  How someone experiences content on the internet can be vastly different depending on the computer or device and size of the screen on which they view it, and how they interact with it.

For example, while some people read text and interpret images they view, others use assistive technology to listen to content using a screen reader.  Meanwhile, some people click on links using a mouse or similar device, while others navigate using a keyboard or by tapping on touch screens.

Improving the accessibility of content is about reducing basic barriers to comprehension, such as providing alternative text for images, so that those who cannot see the images can grasp their meaning.  Similarly, making captions or transcript text available for a video file can make it accessible to someone who cannot hear audio.

For more technical information about making content accessible, see What are some guidelines for making content accessible?