First, what is the SSL Certificate
SSL certificate is a digital certificate, digital certificate by the authority after authority (CA) to verify the site's identity issued, enabling the browser and the server to encrypt data transmission. Security lock symbol appears, the data transfer protocol upgrade from http (traditional protocol) is https (encryption protocol) site in the browser after installation of SSL certificates.
Second, the role of SSL certificates
(1) browser green safety signs
major mainstream browser's emphasis on the website is not installed SSL certificate prompt "unsafe", the installation of SSL certificates web browser will display a green safety signs, the connection is secure. 
(2) data encryption transmission site
after installing SSL certificates, the site is https (encryption protocol) from the upgrade. All data can be encrypted to protect the site, visitor registration information to protect login data, online trading, which is essential for electricity providers, finance, business and other sites.
(3) Safety signs to get visitors trust
OV SSL certificate to verify the true identity of the applicant organization, you can view the details in the certificate applicant. Advanced EV SSL Certificates can also display green business name, visitors can deepen trust the site, browse more confidence in using the browser address bar. 
(4) a strong level of encryption to protect
the SSL certificate has been able to perform data encryption, and its 2048-bit encryption technology are inseparable, always protect this sensitive data.
(5) is conducive to improve the search rankings
Google and Baidu has said publicly before, priority-friendly display https site, which will benefit the website SEO keyword ranking for the website optimization is a great opportunity. 
(6) is compatible with almost popular browsers and devices
SSL digital certificate security SSL Certificates Symantec, Geotrust, Comodo, Thawte and RapidSSL and many other institutions of global authority CA, browser compatibility 99.99%, and all major browsers the device can support.
Third, the importance of SSL certificates
（1）SSL证书在搜索引擎的重要性
百度早先年就表示全面支持https站点，百度在国内搜索引擎市场占比率高达77.53%，网站安装SSL证书已经成为一种趋势。
（2）SSL证书对外贸推广的影响
Chrome等主流浏览器对http站点的“不安全”提示，这无疑是给外贸类网站致命的打击，不仅仅是流量的流失，对品牌的影响也是无法估计的。
（3）各种数据泄露对企业网站造成的影响
近年来，各种数据泄露事件频繁发生，绝大部分事件都来自大型流媒体、社交网络、金融机构等网站。在如今的互联网时代，网络安全以及成为全世界关注的问题。
四、SSL证书怎么申请？
SSL certificate is nothing more than the application considered at three levels: brand authentication, the number of domains
(1) SSL certificate brands to consider: very much a global provider of SSL certificates, can provide international certification SSL Certificate Authority does not have much, internationally renowned reliable SSL certificate brands are: Symantec, Geotrust, Comodo, Thawte and RapidSSL SSL certificates and other foreign brands, you can find security in SSL certificates.
(2) SSL certificate authentication considerations: SSL certificate has three authentication methods, DV SSL certificate (domain verification), OV SSL certificate (tissue verification), EV SSL certificate (Extended Validation), the following differences:
DV the SSL certificate (Domain verification ): only verifying domain ownership, 10 minutes fast issuance, cheap, suitable for individual users, small businesses apply for installation;
OV SSL certificate (organization verification): verifying domain ownership and the applicant organization's true identity, you can view applicant in the certificate details in name, business type for users to install applications;
EV SSL certificate (extended validation): the highest level of verification, verify domain ownership, corporate real legal information, telephone interviews and so verification can be green business name in the browser address bar.
(3) the number of domain SSL certificate consideration: SSL Certificates can be divided into single-domain SSL Certificates, multi domain SSL certificates, wildcard certificate; If you have multiple domain names do not have a website a certificate to apply for multi-domain SSL certificate or wildcard certificate can protection of domain names, not only save the cost of purchasing an SSL certificate, and save time to apply SSL certificate.