These are genereic build instructions
When you run the ./configure scripts you are telling the software and make what options to use when building the source.
"make" will create binaries, libraries, config files, docs, man pages, whatever in the source tree where you built it.
"make install" will install the stuff you just built to the paths defined by the configure scripts (which either used the defaults or the options you passed to the ./config script).
For example - If i build the apache-1.3.27 in /usr/src/packages/apache-1.3.27 nothing gets 'installed' until I run the make install script. After installing it will put apachectl in /usr/bin and any libraries in /usr/libexec and the httpd in /usr/local/apache/bin