A Mast Head is the title of a magazine. It's almost always at the top because its the first place you look and when its in a rack you can only see the top half of the magazine. The font is also chosen to work with the genre of the magazine, if its quite a laid back magazine the writing can look as if its been handwritten, where as if its a girlly magazine the writing can be quite flirty and swirly. Using lower letters would also show that the magazine is laid back but if its in capitals its as if its shouting out at you, so the magazine would be quite serious most likely to be a factual magazine.
The colour of the font is also important as it can relate to what sex the magazine is aimed at. If the writing is pink its more likely to be aimed at women, likewise for blue being for men. Pink is the stereotypical colour for women.