---
schema_version: "1"
id: b7de51c1210d24187e22b20ee7517510895371779a23a72c3fd262379c15b60f
title: Apex FAQ
collection: admin
version: current
locale: en-us
portal_url: https://docs.salesforce.com/admin/current/en-us/platform/264-0-0/faq_apex.md
canonical_url: https://help.salesforce.com/s/articleView?id=platform.faq_apex.htm&release=264.0.0&type=5
source_site: help.salesforce.com
content_type: documentation
content_hash: 82dcbbe9c400373d9f3f00ada71d90c41ed966051fe3aed9546717232b7b9a66
description: Frequently asked questions about external Web services, supported WSDL Schema types, and differences between a Apex classes and triggers.
products:
  - Salesforce Platform
release: "264"
---
# Apex FAQ

Frequently asked questions about external Web services, supported WSDL Schema types, and differences between a Apex classes and triggers.

### Required Editions

<table class="slds-table slds-table_bordered slds-max-medium-table_stacked slds-m-bottom_small edition"><colgroup><col></colgroup><tbody><tr class=""><td class="slds-cell-wrap" style="vertical-align:top;">Available in: Salesforce Classic (<a href="https://help.salesforce.com/s/articleView?id=xcloud.overview_edition_lex_only.htm&amp;type=5&amp;language=en_US" target="_blank">not available in all orgs</a>) and Lightning Experience</td></tr><tr class=""><td class="slds-cell-wrap" style="vertical-align:top;">Available in: <span id="faq_apex__Apex_Code_editions_text"><a name="faq_apex__Apex_Code_editions_text"></a><strong>Enterprise</strong>, <strong>Performance</strong>, <strong>Unlimited</strong>, <strong>Developer</strong>, and <strong>Database.com</strong> Editions</span></td></tr></tbody></table>

## Can I Call an External Web Service With Apex?

Yes. You can call operations of Web services with Apex. Using the Apex Classes page, you must first generate an Apex class from the WSDL document of the external Web service before you can call its methods.

## What are the Supported WSDL Schema Types for Apex Callouts?

We recommend that you validate the WSDL document and ensure that it contains supported schema types. If a type is not supported by Apex, a callout to a Web service operation may result in an error returned in the callout response , such as “Unable to parse callout response. Apex type not found for element item”.

## What Is The Difference Between Apex Classes And Triggers?

An Apex class is a template or blueprint from which Apex objects are created. Classes consist of other classes, user-defined methods, variables, exception types, and static initialization code A trigger is Apex code that executes before or after specific data manipulation language (DML) events occur, such as before object records are inserted into the database, or after records have been deleted. A trigger is associated with a standard or custom object and can call methods of Apex classes.