SWADM is approximately equal to a school district's enrollment, with extra weight given to districts with higher rates of poverty and more students learning English.
MEII is designed to give more money to districts with a lower median household income and less money to districts with a higher median household income.
LECI is a combination of a number of terms. The most significant of these terms is the Local Effort Factor which increases when a district has a higher local tax rate.
Both the SWADM and the MEII are designed to funnel more money to the districts with less. The final factor is different. The LECI gives state money to districts that are working to help themselves.
For those interested, you can read the text of the law here. You can also download the state's spreadsheet with explanations of the calculations here.