According to Marx and Engels, the European powers are scared of the “spectre” of communism; the term is used to tarnish parties that seek to challenge those in power.
Marx and Engels believe that this fear of communism makes two things clear: firstly, that communism is already a growing power. Secondly, it is time for the communists of various nationalities to explain, in the following manifesto, what they actually believe.
The manifesto is not a technical, academic text; it’s meant to be readable for the general public. Furthermore, it’s supposed to empower the public by telling them what communism actually is—and show them just why communism is growing (and why it should continue to do so).