To use some of the most attractive prompts in the Bash Prompt package, you
need to get and install fonts that support the character sets expected by
the prompts. These are "VGA Fonts," which support different character sets
than regular Xterm fonts. Standard Xterm fonts support an extended
alphabet, including a lot of letters with accents. In VGA fonts, this
material is replaced by graphical characters - blocks, dots, lines. I
asked for an explanation of this difference, and Sérgio Vale e Pace
(space at gold.com.br) wrote me:
I love computer history so here goes:
When IBM designed the first PC they needed some character codes to use, so
they got the ASCII character table (128 numbers, letters, and some
punctuation) and to fill a byte addressed table they added 128 more
characters. Since the PC was designed to be a home computer, they fill the
remaining 128 characters with dots, lines, points, etc, to be able to do
borders, and grayscale effects (remember that we are talking about 2 color
graphics).
Time passes, PCs become a standard, IBM creates more powerful systems and
the VGA standard is born, along with 256 colour graphics, and IBM continues
to include their IBM-ASCII characters table.
More time passes, IBM has lost their leadership in the PC market, and the
OS authors dicover that there are other languages in the world that use
non-english characters, so they add international alphabet support in their
systems. Since we now have bright and colorful screens, we can trash the
dots, lines, etc. and use their space for accented characters and some
greek letters, which you'll see in Linux.
Take our 
