Which of the following experts will explain what these php configurations mean?

Who will explain what these php configurations mean? extension = php_bz2.dll; extension = php_curl.dll; extension = php_fileinfo.dll; extension = php_gd2.dll; extension = php_gettext, who will explain what these php configurations mean?
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; Extension = php_bz2.dll
; Extension = php_curl.dll
; Extension = php_fileinfo.dll
; Extension = php_gd2.dll
; Extension = php_gettext.dll
; Extension = php_gmp.dll
; Extension = php_intl.dll
; Extension = php_imap.dll
; Extension = php_interbase.dll
; Extension = php_ldap.dll
; Extension = php_mbstring.dll
; Extension = php_exif.dll; Must be after mbstring as it depends on it
Extension = php_mysql.dll
; Extension = php_mysqli.dll
; Extension = php_oci8.dll; Use with Oracle 10gR2 Instant Client
; Extension = php_oci8_11g.dll; Use with Oracle 11gR2 Instant Client
; Extension = php_openssl.dll
; Extension = php_pdo_firebird.dll
; Extension = php_pdo_mysql.dll
; Extension = php_pdo_oci.dll
; Extension = php_pdo_odbc.dll
; Extension = php_pdo_pgsql.dll
; Extension = php_pdo_sqlite.dll
; Extension = php_pgsql.dll
; Extension = php_pspell.dll
; Extension = php_shmop.dll

The MIBS data available in the PHP distribution must be installed.
; See http://www.php.net/manual/en/snmp.installation.php
; Extension = php_snmp.dll

; Extension = php_soap.dll
; Extension = php_sockets.dll
Extension = php_sqlite3.dll
; Extension = php_sybase_ct.dll
; Extension = php_tidy.dll
; Extension = php_xmlrpc.dll
; Extension = php_cmd.dll
; Extension = php_zip.dll


------ Solution --------------------
You only open
Extension = php_mysql.dll; MySQL database operation function Group
Extension = php_sqlite3.dll; SQLite3 database operation class

If you do not use other products, do you want to explain them?

------ Solution --------------------
Here is the link for you.
Http://www.php.net/manual/zh/extensions.php