How to get store information in Magento?

Get store data

Mage::app()->getStore();

Store Id

Mage::app()->getStore()->getStoreId();

Store code

Mage::app()->getStore()->getCode();

Website Id

Mage::app()->getStore()->getWebsiteId();

Store Name

Mage::app()->getStore()->getName();

Store Frontend Name (see @Ben's answer)

Mage::app()->getStore()->getFrontendName();

Is Active

Mage::app()->getStore()->getIsActive();

Homepage URL of Store

Mage::app()->getStore()->getHomeUrl();

Current page URL of Store

Mage::app()->getStore()->getCurrentUrl();

All of these functions can be found in class Mage_Core_Model_Store

File: app/code/core/Mage/Core/Model/Store.php

To get information about the current store from anywhere in Magento, use:

<?php
$store = Mage::app()->getStore();

This will give you a Mage_Core_Model_Store object, which has some of the information you need:

<?php
$name = $store->getName();

As for your other question about line number, I'm not sure what you mean. If you mean that you want to know what line number in the code you are on (for error handling, for instance), try:

<?php
$line      = __LINE__;
$file      = __FILE__;
$class     = __CLASS__;
$method    = __METHOD__;
$namespace = __NAMESPACE__;

Great answers here. If you're looking for the default view "Store Name" set in the Magento configuration:

Mage::app()->getStore()->getFrontendName()