What is the difference between Project Leader and Project Manager?

They're related, but have a different focus:

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      A project leader will typically be responsible for more of the day-to-day running of the development effort. They should have a more technical focus than a project manager, and they're more likely to be involved in helping determine software architecture, release details, etc. A development team's senior developer or senior architect will often fill the role of the project leader in this respect.
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      A project manager will typically be more focused on the business side of the development effort, so they're going to be talking about meeting business requirements, managing development budgets, etc. Less of the day-to-day technical stuff and more of the fluffy business stuff.