Rigor in the 6-12 ELA and Social Studies Classroom by 
Common Core Curriculum Maps in English Language Arts, Grades 6-8 by 
Common Core Curriculum: English, Grades 9-12 by Practitioner journals differ from research journals in that they feature articles written primarily by professionals in a given field (in this case, teachers!). These articles often feature real-life experiences or observations, and are geared towards offering advice, establishing best practices, and noting trends within the field. Articles may still be scholarly, but they are not always necessarily reporting original research.
Research journals differ from practitioner journals in that they typically feature original scholarly work. Articles are more likely to be primary sources, featuring the methods and results of a study conducted by the author(s). Research journals are almost always peer-reviewed.
You may notice that some of the journals are listed twice, with different dates listed after them. This means that different issues or volumes of the journal are available through different databases - so for example, one database may only offer issues published before 2005, and another only issues of the same journal published after 2001. Older issues may be useful if you are looking for seminal works, while newer issues will be useful for keeping up to date on trends in the field.