The way Gmail can be organized, a label can be a tag, but it can also be a folder.
Gmail also very confusing. Labels don't always behave like folders, but sometimes they do. Because you can attach multiple labels to a conversation, you have a lot more options.
(Remember that Gmail, by default, organizes not by individual messages, but by conversations, each of which contains an original message and all replies to that message.)
In a folder-based email client like Outlook, you can move an email from your inbox, say, to a folder called SecNews. When you do that, the message disappears from your inbox. Like a physical object, it can't be in two places at once.
But you can put any number of labels on a physical object and in a Gmail. You can put a label “SecNews” on a conversation and it will appear in both the SecNews folder and your Inbox.
If you don't want it in your Inbox, just click the "Archive" button. You can still archive a conversation without labels.
Many people use labels like folders, and Gmail makes this scenario easy. The Gmail toolbar has a “Move to” icon that looks like a Folder and a corresponding “Labels” icon that looks like a label.
When you use the Labels tool, Gmail assigns the label you choose to the conversation. Other labels, including Inbox, remain.
But when you use the “Move to” tool, it assigns the label you chose for that particular conversation and removes all existing ones. More generally speaking, and if not technically incorrect, it moves it to another folder.
The same thing happens when you drag a message to the label list in the left pane. Drag a message to SecNews and Gmail will add the SecNews while removing all other labels, including Inbox. (Unfortunately, when you drag from another label to Inbox, both labels remain in the conversation.)
So, don't miss the opportunity to organize emails . Start now!
