Intermediate Certificates help complete a "Chain of Trust" from your SSL or Client Certificate to GlobalSign's Root Certificate.
As an OrganizationSSL customer you must install your end entity SSL Certificate (received via e-mail) along with an OrganizationSSL Intermediate Certificate listed below.
Instructions for installing SSL Certificates on various platforms can be found here:
Note: In some cases, the web server may need to be configured with the GlobalSign R3-R5 Cross Certificate or possibly with Root R3 or Root R5 as part of the standard configuration process.
If you want browsers to chain up to Root R3, a SHA-256 Root, instead of Root R1, a SHA-1 Root, then you must install this Intermediate Certificate on your web server instead of the one provided with the Certificate. Note: This Intermediate Certificate has the same keys and same Certificate SubjectDN and will use this when provided in the TLS session so that their connections chain up to Root R3.