SSL certificate install ... .pfx, .cer and .txt files?

While I know nothing about SSL or installing SSL Certificates, I'm sure one of the many results Google will 开发者_StackOverflow社区give me for CentOS, SSL certs and Apache would help.

However, the certificate files which have been provided for this project are a .pfx file, .cer (the certificate) file and a .txt (apparently a certificate request) file, none of which are mentioned in the articles I'm finding.. they all talk of .crt and .key files.

Is there a particular way I should be converting these files, presumably via openssl, into something I can use in Apache?

.pfx files tend to be PKCS#12 files (which will contain the private key, the certificate and possibly the issuer certificate chain). They're sometimes called .p12. OpenSSL can extract private key and certificate from PKCS#12 files (via its openssl pkcs12 command), you should be able to find documentation to do this, via Google or other questions on SO.