transmission FTIR v. reflectance FTIR

Dear Group,
I am new to this group, but this site was recommended by a carbon research association. I was hoping someone here might be able to give
me a concise explanation of the difference between transmission FTIR and reflectance FTIR. I am preparing to do some FTIR research on activated carbon, and I'm having some difficulty with information overload. I went to the library to find literature on the subject, and it all seemed very confusing.
Thank you for your help. Any insight into the problem would be much appreciated.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
Add image file
Upload is a website by engineers for engineers. It is not affiliated with any of manufacturers or vendors discussed here. All logos and trade names are the property of their respective owners.