So freedom is one of the core principles within liberalism, and it can be used interchangably (instead of) the word liberty. There are many types of freedoms, such as economic, political and socially - which overall all liberals champion, however, they disagree as to what extent and in what way they wish to pursue these given freedoms. This split, caused Mill to identify two broad approaches to freedom: positive and negative - however Berlin was the one who actually came up with the name! Negative freedoms are largely favoured by classical liberals, and can be more commonly simplified as 'freedom from'. This really is what it sounds: classical liberals wanted 'freedom from' various social shackles, such as economic management from government, too many laws, and limits on freedom of speach and religion. They therefore wanted a laissez-faires (low regulation) economy, a 'nightwatchman state' (a term used by Locke that simply means low government interference with its citizens), and tolerance for every person. If you would like a quote to summarise their beliefs and to elevate your essay, take Constant: 'the aim of moderns is the enjoyment of security in private pleasures'.
On the contrary, positive freedoms are favoured by modern liberals. Positive freedom is often known as 'freedom to' acheive something. It was first promoted by T. H. Green, who rejected the classical liberal claim that humans should only be concerned with their freedom, and instead should look to promote their neighbours freedom, that may often be lower than theirs. For example, take two 18 year olds, wanting to go to the same university: the first, has been privately educated, has a mother who cooks a well balanced meal a day and has access to all the right materials to do his exam. The second, has been to their local failing school, lives off junk food, and has one disinterested parent in their education. A modern liberal would argue the second has a lower chance of succeeding and therefore a lower 'freedom to' or positive liberty, they would therfore advocate some government interference in order to increase his freedom; for example, higher grants to his failing school, a free nutritious school meal, and a free afterschool homework club with someone to help him in a way his parent is unable to. Overall, a governments pursuit of positive freedoms will lead to some form of a wellfare state. To make your essay better, an example of a government implimenting positive freedoms are: William Beverdige's 5 giants and the 1945 welfare reforms; and the New Labour ethos. The latter example also shows us how positive freedoms are not exclusive to liberalism.