As a researcher it is important that you understand copyright and how it affects your research impact. When you publish, depending on the publisher's policy, you may have to sign the copyright over to the publisher . This will affect whether the you can copy the work, for students for example, or whether you can deposit in a open access repository.
In your own research you must adhere to good copyright practice.
What rights you transfer to the publisher will be agreed by the contract you make with them. The publisher will usually specify what rights are being transferred from you to them. You should understand that it is not an all or nothing situation.
The transfer will allow you to retain some rights for redistribution of your work, including in some instances making it available in open access by either full open access of putting it into a repository.
Copyright law applies to all authors. However there is some more caveats when it comes to researchers.
For instance figures can be used under the ICLA license as long as they are not significant overall but highly significant to the passages you are trying to copy. If is under excluded works you will need to get permission. Depending on your contact with publisher you may also need to do this for your own previous work as if you signed over the copyright you are no longer the copyright holder keep this in mind when making the contracts.
SHERPA RoMEO provides a searchable database of journals copyright policies so you can understand what they mean for any work you publish in journals.
A basic introduction to copyright and its relation to the work of researchers.
The Library, Technological University of the Shannon: Midwest